Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Deoxyadenosine and deoxyguanosine are toxic to human lymphoid cells in culture and have been implicated in the pathogenesis of the immunodeficiency states associated with adenosine deaminase and purine nucleoside phosphorylase deficiency, respectively. We have studied the relative incorporation of several labeled nucleosides into DNA and into nucleotide pools to further elucidate the mechanism of deoxyribonucleoside toxicity. In the presence of an inhibitor of adenosine deaminase [erythro-9-(2-hydroxy-3-nonyl)adenine [EHNA], 5 muM], deoxyadenosine (1-50 muM) progressively decreased the incorporation of thymidine, uridine, and deoxyuridine into DNA, but did not affect uridine incorporation into RNA. This decrease in DNA synthesis was associated with increasing dATP and decreasing dCTP pools. Likewise, incubation of cells with deoxyguanosine caused an elevation of dGTP, depletion of dCTP, and inhibition of DNA synthesis. To test the hypothesis that dATP and dGTP accumulation inhibit DNA synthesis by inhibiting the enzyme ribonucleotide reductase, simultaneous rates of incorporation of [(3)H]uridine and [(14)C]thymidine into DNA were measured in the presence of deoxyadenosine plus EHNA or deoxyguanosine, and in the presence of hydroxyurea, a known inhibitor of ribonucleotide reductase. Hydroxyurea (100 muM) and deoxyguanosine (10 muM) decreased the incorporation of [(3)H]uridine but not of [(14)C]thymidine into DNA; both compounds also substantially increased [(3)H]cytidine incorporation into the ribonucleotide pool while reducing incorporation into the deoxyribonucleotide pool. In contrast, deoxyadenosine plus EHNA did not show this differential inhibition of [(3)H]uridine incorporation into DNA, and the alteration in [(3)H]cytidine incorporation into nucleotide pools was less impressive. These data show an association between accumulation of dATP or dGTP and a primary inhibition of DNA synthesis, and they provide support for ribonucleotide reductase inhibition as the mechanism responsible for deoxyguanosine toxicity. Deoxyadenosine toxicity, however, appears to result from another, or perhaps a combination of, molecular event(s).
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PMID:Purinogenic immunodeficiency diseases. Differential effects of deoxyadenosine and deoxyguanosine on DNA synthesis in human T lymphoblasts. 11 1

Hydroxyurea, an inhibitor of ribonucleotide reductase, blocks replication of vaccinia virus. However, when medium containing hydroxyurea and dialyzed serum was supplemented with deoxyadenosine, the block to viral reproduction was circumvented, provided that an inhibitor of adenosine deaminase was also present. Deoxyguanosine, deoxycytidine, and deoxythymidine were ineffective alone and did not augment the deoxyadenosine effect. In fact, increasing concentrations of deoxyguanosine and deoxythymidine, but not deoxycytidine, eliminated the deoxyadenosine rescue, an effect that was reversed by the addition of low concentrations of deoxycytidine. These results suggested that the inhibition of viral replication by hydroxyurea was primarily due to a deficiency of dATP. Deoxyribonucleoside triphosphate pools in vaccinia virus-infected cells were measured at the height of viral DNA synthesis after a synchronous infection. With 0.5 mM hydroxyurea, the dATP pool was greater than 90% depleted, the dCTP and dGTP pools were 40 to 50% reduced, and the dTTP pool was increased. Assay of ribonucleotide reductase activity in intact virus-infected cells suggested that hydroxyurea may differentially affect reduction of the various substrates of the enzyme.
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PMID:Deoxyadenosine reverses hydroxyurea inhibition of vaccinia virus growth. 201 60

Hydroxyurea-resistant S49 T-lymphoma cells have increased ribonucleotide reductase activity and deoxyribonucleoside triphosphate pools when compared with wild-type cultures. If ribonucleotide reductase inhibition is the mechanism by which deoxyadenosine is cytotoxic, then hydroxyurea (HU)-resistant S49 cells might be more resistant to deoxyadenosine toxicity when adenosine deaminase is inhibited than wild-type cells. Five S49 cell lines resistant to varying concentrations of HU were compared with wild-type cells by measuring CDP reductase activity, deoxyribonucleoside triphosphate pools, and deoxyadenosine toxicity. All five cell lines resistant to increasing concentrations of HU exhibited a twofold increase in resistance to deoxyadenosine toxicity when compared to wild type, and the resistance was proportional to the twofold increased pools of dNTPs in these cell lines but was less than the six- to eight fold increase in ribonucleotide reductase activity. In both wild-type and mutant cell lines, deoxyadenosine toxicity was accompanied by the accumulation of deoxyadenosine triphosphate and reduction of the other dNTPs; however, only dGTP greatly diminished. Exogenous addition of deoxycytidine decreased the dATP accumulation by about 20%, but also resulted in increases in the dCTP, dTTP, and dGTP pools. The S49 cells arrested in G1 phase when exposed to dAdo, although hydroxyurea-resistant cells required higher dAdo concentrations to elicit G1-phase arrest than wild-type cells. Deoxycytidine prevented dAdo-induced G1 arrest in all cell types. In summary, these data support the hypothesis that deoxyadenosine-induced dATP accumulation results in inhibition of ribonucleotide reductase and that this may be the mechanism for both cell cycle arrest and cytotoxicity in S49 T-lymphoma cells.
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PMID:Deoxyadenosine toxicity and cell cycle arrest in hydroxyurea-resistant S49 T-lymphoma cells. 305 32